title: Evaluation of in vivo genotoxicity induced by N-ethyl-N-nitrosourea, benzo[a]pyrene, and 4-nitroquinoline-1-oxide in the Pig-a and gpt assays.
abstract: The recently developed Pig-a mutation assay is based on flow cytometric enumeration of glycosylphosphatidylinositol (GPI) anchor-deficient red blood cells caused by a forward mutation in the Pig-a gene. Because the assay can be conducted in nontransgenic animals and the mutations accumulate with repeat dosing, we believe that the Pig-a assay could be integrated into repeat-dose toxicology studies and provides an alternative to transgenic rodent (TGR) mutation assays. The capacity and characteristics of the Pig-a assay relative to TGR mutation assays, however, are unclear. Here, using transgenic gpt delta mice, we compared the in vivo genotoxicity of single oral doses of N-ethyl-N-nitrosourea (ENU, 40 mg/kg), benzo[a]pyrene (BP, 100 and 200 mg/kg), and 4-nitroquinoline-1-oxide (4NQO, 50 mg/kg) in the Pig-a (peripheral blood) and gpt (bone marrow and liver) gene mutation assays. Pig-a assays were conducted at 2, 4, and 7 weeks after the treatment, while gpt assays were conducted on tissues collected at the 7-week terminal sacrifice. ENU increased both Pig-a and gpt mutant frequencies (MFs) at all sampling times, and BP increased MFs in both assays but the Pig-a MFs peaked at 2 weeks and then decreased. Although 4NQO increased gpt MFs in the liver, only weak, nonsignificant increases (two- or threefold above control) were detected in the bone marrow in both the Pig-a and the gpt assay. These findings suggest that further studies are needed to elucidate the kinetics of the Pig-a mutation assay in order to use it as an alternative to the TGR mutation assay.
authors.affiliation: Division of Genetics and Mutagenesis, National Institute of Health Sciences, Setagaya-ku, Tokyo, Japan.
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Horibata
authors.forename: Akiko
authors.initials: A
authors.lastname: Ukai
authors.forename: Takafumi
authors.initials: T
authors.lastname: Kimoto
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Suzuki
authors.forename: Nagisa
authors.initials: N
authors.lastname: Kamoshita
authors.forename: Kenichi
authors.initials: K
authors.lastname: Masumura
authors.forename: Takehiko
authors.initials: T
authors.lastname: Nohmi
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Honma
mesh_terms: D015112:4-Nitroquinoline-1-oxide / Q000633:toxicity*; D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D001681:Biological Assay; D004249:DNA Damage / Q000187:drug effects*; D004912:Erythrocytes / Q000187:drug effects*; D029968:Escherichia coli Proteins / Q000502:physiology*; D005038:Ethylnitrosourea / Q000633:toxicity*; D005434:Flow Cytometry; D008099:Liver / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation / Q000235:genetics; D010430:Pentosyltransferases / Q000502:physiology*
chemical_list: D029968:Escherichia coli Proteins; D009153:Mutagens; D001564:Benzo(a)pyrene; D015112:4-Nitroquinoline-1-oxide; D010430:Pentosyltransferases; C071962:Gpt protein, E coli; D005038:Ethylnitrosourea
keywords: genotoxicity; glycosylphosphatidylinositol anchor; red blood cells; transgenic rodent mutation assays